I personally like them, as I've never been a super big fan of the Yahoo Groups - though they have fit the bill for some other projects and groups that I've belonged to in the past.

Only feature I liked was the Daily Digest Emails from them with message content included, that made things great.

Subscribing to topic works okay for individual topics and checking the Subscribe to forum link under each individual forum (General < Announcements, Development < New Sources, etc). I was hoping to be able to Subscribe to General, Development, etc and have it do it for all forums and topics under that.